Sear mechanism



W. R. WEEKS SEAR MECHANISM Filed Sept. 26, 1946 Dec. 26, 1950 Inventor Walt er fl-Weeks Patented Dec. 26, 1950 UNITED STATES PATENT OFFICE SEAR MECHANISM Walter- R. Weeks, Hamden, Conn., assignor to General Electric. Company, a corporation of:

NewYork,

Application September 26, 1946, Serial No. 699,399

(Cl. .42.--G9.)

2 Claims.

My mventim relates to. a sear mechanismL more particularly to a. scar mechanism for automatic: guns. and has for its object simple and? in which the bolt. is retained in a. gun-um loaded or or Battery position until the gun is. to. be; fired. atv which time: the. sear mechanism isoperated; to. release the bolt- It; will be. understood that. in, automatic; guns;

especially machine guns of" substantial. size, the bolt. of the gun is thrown back upon the firing of the; gun with a. tremendous. force and. the bolt, arter striking the recoil or: buffer spring; is moved: forward. with a tremendous force.

In; accordance with my invention. in one form I provide a pivoted: latching arm having a latchmgv when on one end and having its other end' mounted on'apivot'pinwhich is movable against.

the force of a spring so that. when the roller engagedby the gun; bolt: the roller arm and pivot pin are moved against the spring force for a predetermined distance- I have also provided a latching, stop. for the latching armior. preventing movement ofthe arm to a released position, this.

stop-bein engaged by the roller after the roller has been moveda slight distance by the gun bolt.

For. a morecomplete understanding of my in. vention reference. should be made to the drawing; 1 of which is a. fragmentary view, partly in section, of scar mechanismemboch ing my inventitan;v 2-

a fragmentary plan view ofi Fig; I; Fig. 3 is a view similar to Fig. l but showing the sear mechanism in the bolt-released position, while Fig. i's' a view similar to Fig. 1 but showing the position of the parts of the sear mechanism at the instant the bolt is stopped by the sear mechanism.

Referring to the drawing, I have shown my invention in one form as applied to the latching and securing the gun bolt I mounted for rectilinear movement in a predetermined path from the left hand, as viewed in Fig. 1, toward the right hand and vice versa. When the gun is fired it will be understood that the bolt I is thrown by th force of the explosion toward the left hand to an extreme position into engagement with a recoil or buffer spring (not shown) from which it rebounds and moves toward the right hand a short distance and is secured in the gun-unloaded position shown in Fig. 1 by the sear mechanism 2. When the gun is to be fired the sear mechanism isoperated to release the bolt whereupon the bolt. is moved by a suitable spring: (not shown) in: a

right hand direction to the loading position, the gun breach mechanism is locked. in place, and the In. accordance: with my invention the sear mechanism 2 comprises a. latching roller 3 mountedon a u-shaped arm or: frame 4 provided with a pivot. pin. 5. The arm 4 and the. roller 3 are biased about the pivot pin 5 in a clockwise direction to a bolt latching position by a spring 6. until a projection I on the arm 4 engages a stop pin 8 as shown in Fig.- 1. In this position the roller 3- engages a projection. 9 on the bolt I.

. thereby latching and holding the bolt in its gununloaded position as shown. In order to release the. bolt, the arm i.- is turned, counterclockwise by means of a link member ID having an elongated. aperture H into which projects, a pin I2 on the arm 4. When the gun is to be. fired the link I0 is moved toward the left hand, thereby to turn the arm 4 counterclockwise against the force of the spring 3 to the. position shown in Fig. 3, whereby the bolt is released.

For the purpose of normally positioning the pin 5 as well as the roller 3 and arm 4 in one extreme position as shown in Fig. I, I. provide a heavy helicalspring l3'of suitable strength which ismounted in. a bore It in a. metal block member 'j I5; The. block I5 is secured rigidly to the frame I6 ofthe gun by means of. two screws I1. Moreover, the block I5 is provided with an arcuate concave surface I8. extending parallel with the roller 3 having substantially the same curvature,

- as the surface of, the. roller, and with an aperture Is for the pivot pin 5 having a diameter considerably greater than the diameter of the pin, about fifty percent greater as shown in the drawing. Normally, the pin 5 is biased toward the left hand by the spring I3 along a path substantially parallel with the path of movement of the bolt I against the left hand wall of the aperture I9, the right hand end of the spring bearing against the stop member 20 on the block I5 and its left end being provided with a plunger-shaped member having a shank 2 I fitting inside the spring I3 and an outer head 22 slidably fitting in the bore I4. In the head 22 is a semi-circular groove 23 extending diametrically across its face into which fits the pin 5.

When the bolt I is thrown toward the left hand upon firing of the gun its projection 9 moves past the roller 3 depressing the roller and thereupon the roller is moved back to engaging position by the spring 6 so as to secure the bolt when it moves back again after engaging the buffer spring of the gun. The bolt is thrown from the buffer spring toward the right hand at a very high speed and strikes the roller 3 with a tremendous force, pushing the roller 3, the arm or frame 4, and the pin toward the right hand against the force of the spring [3 until finally the roller is stopped by abutting engagement with the curved surface l8. After the bolt has thus been stopped the spring l3 moves the pin 5 toward the left hand, and with it the arm 4, roller 3, and the bolt I to the positions shown in Fig. 1. In this position the roller 3 may be moved to release the bolt by the firing member II].

An important feature of my invention is the positioning of the curved surface l8 so as to catch the roller 3 and prevent downward movement of the roller after the roller has been moved toward the right hand a very short distance, at which time the lower side of the roller strikes the lower lefthand edge or projection 24 of the surface I8. Therefore, the surface i8 acts as a positive stop to prevent downward movement of the roller and thereby makes possible the use of a comparative-' 1y weak biasing spring 6 whereby a correspondingly small force is required to move the roller 3 downward in the release of the bolt. The spring 6 need be strong enough only to turn upward the arm 4 and roller 3 to the latching position of Fig.- 1 in time to catch the bolt as it moves back toward the right hand after engaging the buffer spring. The spring i3, while yielding to provide for engagement of the roller 3 with the surface I8, is strong enough to assure the normal positioning of the parts as shown in Fig. 1. I

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention. What I claim as new and desire to secure by Letters Patent of the United States is:

1. Latch meehanismcomprising an arm, a pivot for one end of said arm, a latching roller on the opposite movable end of said arm, supporting means for said pivot arranged to provide forlimited movementof said pivot in a predetermined path, a first spring for normally biasing said .pivct, arm, and roller in a predetermined direction along said path to predetermined positions, a second spring for biasing said arm and roller about said pivot to a predetermined latching position, means for turning said arm about said pivot against the force of said second spring to a released position, and a rigid stop member for said roller normally spaced from said roller to provide for movement of said roller about said pivot to said released position when said pivot is in its said predetermined position, said stop member being provided with a concave surface in position to be abuttingly engaged by'said roller and bring said latching member to rest when said roller is moved a predetermined distance along said predetermined path against the force of said first spring.

2. Sear mechanism for securing a gun bolt movable in a predetermined path comprising an arm, a pivot for one end of said arm, a bolt latchingroller on the opposite movable end of said arm, supporting means for said pivot arranged to provide for limited movement of said pivot in a path substantially parallel with said predetermined path, a first spring for normally biasing said pivot, arm, and roller in a predetermined direction along its said path to predetermined posi-- tions, a second spring for biasing said arm and.

roller about said pivot to a predetermined latch ing position, means for turningsaid arm about a said pivot against the force of said second spring to a released position, a rigid stop member for said roller normally spaced from said roller to provide for movement of said roller about said pivot to said released position when said pivot is in its said predetermined position, said stop mem-' ber being provided with-a concave surface abut-.i

tingly engaged by said roller to bringsaid roller to rest when said roller is moved by the gun bolt a predetermined distance along said predetermined path against the force of said first spring, and a projection on said stop member forming a. continuation of said concave surface extending toward said latching member on the side of said roller toward which said roller moves to saidreleased position and engaged by said roller thereby to prevent movement of said roller about said pivot from said latching position.

WALTER R. WEEKS.

REFERENCES CITED The following references are of record irr file of this patent: I t

' UNITED STATES PATENTS- Date Birkigt NOV. 14, 1939 

